development of a multi feed pelletizer for the production...

American Journal of Mechanical and Materials Engineering

2017; 1(2): 44-48

http://www.sciencepublishinggroup.com/j/ajmme

doi: 10.11648/j.ajmme.20170102.13

Development of a Multi Feed Pelletizer for the Production of Organic Fertilizer

Ilesanmi Afolabi Daniyan*, Omokhuale Marcus Akhere

Department of Mechanical & Mechatronics Engineering, Afe Babalola University, Ado-Ekiti, Nigeria

Email address:

[email protected] (I. A. Daniyan) *Corresponding author

To cite this article: Ilesanmi Afolabi Daniyan, Omokhuale Marcus Akhere. Development of a Multi Feed Pelletizer for the Production of Organic Fertilizer.

American Journal of Mechanical and Materials Engineering. Vol. 1, No. 2, 2017, pp. 44-48. doi: 10.11648/j.ajmme.20170102.13

Received: March 13, 2017; Accepted: April 15, 2017; Published: June 2, 2017

Abstract: Organic fertilizer is the end product obtained by converting organic wastes such as crop residue, urban waste,

poultry dropping and animal dung etc. into a useable fertilizer by composting. In this study, a screw type multi feed pelletizing

machine was designed and fabricated. The machine essentially consists of a single phase 3 kW electric motor, 50 mm shaft,

screw auger, pelletizer barrel, ball bearing, pulley, 8 mm thick V-belt. The dimension of the machine frame is 800 × 500 × 600

mm. The shaft transmits motion by means of a 3 kW electric motor. The output pellet was formed by compacting the compost

through a die opening by a mechanical process. The performance of the machine was based on pelleting efficiency, percentage

recovery and throughput capacity of the machine, which was determined at three different mesh sizes; 6 mm, 4 mm and 2 mm.

The total mass of pellets was observed to increase as mesh size increases, hence pelleting efficiency increases as mesh sizes

increases.

Keywords: Composting, Organic Waste, Multi Feed, Organic Fertilizer, Pellet

1. Introduction

Organic fertilizers are necessary for proper growth and

development of plants. Organic-based fertilizers partly solves

waste disposal problems through conversion of

biodegradable wastes into organic compost ensuring the

availability of organic fertilizer for soil conditioning (Moore

et al., 1991; Mansell et al., 1981). It help check soil erosion

by improving the soil structure and increasing the moisture

holding capacity of the soil (Hochmuth et al., 1997) and can

convert carbon losses into the gain particularly due to the use

of green manure thereby increasing soil fertility. It can also

be used as supplements to chemical fertilizers, thereby

reducing the import of the chemicals (Mansell et al., 1981).

Organic fertilizer is the end product obtained by converting

organic wastes such as crop residue, urban waste, poultry

dropping and animal dung etc. into a useable fertilizer by

composting. Fresh composted manure generally has high

nitrogen content than composted manure. However, the use

of composted manure will contribute more to the organic

matter content of the soil. Fresh manure is high in soluble

forms of nitrogen which can lead to sand build up and

leaching. If over applied it can introduce pathogens and

viable weed seed into the soil. Organic material such as

livestock and poultry manure, food waste and yard waste can

be composted to provide an improved product for soil

application or upgraded use such as horticultural planting

mixtures and hydroponics applications. The objective of

composting is to provide a proper nutrient balance and

environment for the reproduction of aerobic thermophilic

bacteria. Factors such as temperature, moisture content,

structure, and proper aeration are critical to efficient

composting. Operating temperatures of 55 to 65oC are

desirable during the aerobic composting process. These

temperatures kill fly larvae, pathogens, and weed seeds.

Composting is a biological process in which organic wastes

are broken down by microorganism and converted into a

product to be used as a soil conditioner known as organic

fertilizer. This process depends upon the activity of

microorganism. These microorganisms require a carbon to

nitrogen ration (C:N) between 25 -30 moisture content of 40-

60%, pH between 5 and 12 and particle size greater than 30%

free air space (Wilson,1989) when manure is composted, its

volume decreases and nutrient density increases (Holden,

45 Ilesanmi Afolabi Daniyan and Omokhuale Marcus Akhere: Development of a Multi

Feed Pelletizer for the Production of Organic Fertilizer

1990). Nowadays, organic-based agricultural production is

the rapidly emerging technology which partly solves waste

disposal problems through conversion of biodegradable

wastes into organic compost while ensuring the availability

of organic fertilizer (Moore et al., 1991). The development of

an organic fertilizer pelletizer will make it possible to

produce organic fertilizer in different sizes. It will also

generate a design database for small, medium and large scale

fertilizer plant thereby enhancing production of organic

fertilizer for restoring lost fertility to the soil. This will boost

crop production. The production process of organic fertilizers

include: collection of organic wastes from various localities

(agricultural fields, gardens, animal farms; etc.); composting

of these materials to obtain the desired carbon to nitrogen

ratio; size reduction in a ball mill, blending, impregnation of

desired microbial culture, pelletization, drying, and bagging.

The process flow for production of organic fertilizer from

organic wastes is described in Figure 1.

Figure 1. Process Flow for the Production of Organic Fertilizer.

2. Method

The work comprises of design, fabrication and

performance evaluation of the pelletizer.

2.1. Design and Fabrication of the Pelletizer

Pellets are produced by the process of extrusion.

According to Hammed (2013), pelletizing of powdery

fertilizer has potential to kill pathogens and enteric parasites.

It can also reduce the impact of biological aerosols (bio

aerosols) and endotoxins on the manufactures and the end

users. According to Reza-Bagheri et al. (2011) pellet is safer

due to removal of these pathogens and is easier to handle,

store, transport and apply than powder organic fertilizer

(Hammed, 2013; Erickson and Prior, 1990; Hernandez et al.,

2006). Aremu et al. (2014) reported that pelletizing can be

achieved using extrusion machines which include the rotary

pelletizer, the screw type and the hydraulic press however,

the most widely used method is the screw type in which the

raw materials oil are pressed in a perforated chamber. The

developed pelletizing machine consists of the hopper through

which the compost is fed into the machine and a worm screw

(shaft) which propel a dense mass of compost through a

small die opening. The shaft transmits motion by means of a

3 kW electric motor. The output pellet is formed by

compacting the compost through a die opening by a

mechanical process. The design involves the determination of

the pelletizer geometry and capacity as well as the choice of

construction material. The following are design

considerations: system capacity, hopper capacity, power

requirement, forces acting on the shaft and shaft diameter.

2.1.1. System Capacity

The first design consideration is the pelletizer capacity

which is determined by the mass balance of input and output

throughputs. The sum of the volume of all throughput

entering the pelletizer gives the total volume of the pelletizer

for one batch. In order to meet a daily production of 250 kg

of organic fertilizer, production is calculated as 10 kg per

hour. To meet the targeted production capacity, the volume of

the pelletizer is calculated as 0.24 m3. The mass of the

compost per batch is given by equation 1.

( )mass

densityvolume

ρ = (1)

The density of the compost is 350 kg/m3, volume of

pelletizer (0.24 m3)

Hence, mass of compost is calculated as 84 kg.

2.1.2. Hopper Design

The pelletizing machine comprises of some basic

component such as the hopper which feed manure into the

machine, to the pelleting chamber which consists of the

worm, auger or screw (shaft) which propel the manure. The

hopper is in form of rectangular based pyramid frustum,

which is made of mild steel.

The selected dimensions are:

i. Upper face of the hopper: 260 mm x 240 mm

ii. Lower face of the hopper: 70 mm x 50 mm

iii. Height: 150 mm.

The development of the hopper is such that the dimensions

are marked out and cut out from a mild steel sheet, then

welded together. Pellets are produced through the process

called extrusion. The shaft transmits motion by means of a 2

kW electric motor. The output pellet is formed by

compacting and forcing it through a die opening (with

suitable diameter die hole) by a mechanical process.

The inner diameter d1 = 10 mm and the outer diameter d2 =

15 mm. With a thickness 2 mm, the ratio of thickness t to

American Journal of Mechanical and Materials Engineering 2017; 1(2): 44-48 46

inner diameter ratio is t/d1 = 0.20. A cylinder with t/d1 < 0.05

is generally regarded as a thin walled cylinder (Ryder, 1997).

Thus, this pelleting cylinder is a thick walled cylinder.

The internal pressure which is equal to the extrusion

pressure is given by equation 2.

� � �� (2)

where; P is the design extrusion force (10 kN), A is the bore

area 0.0201 m2, hence the internal pressure is calculated as

476 kN/m2 from equation 4. According to Khurmi (2010),

the maximum tensile strength of mild steel plate is given as

250 N/mm2. Using a safety factor of 1.5, the circumferential

stress is calculated as 166.66 N/mm2.

2.1.3. Worm Screw

The worm screw specified has a pitch diameter, Dp = 20

mm, and thread pitch pt = 10 mm. According to

Doboronoslky et al. (1977), the design for thread wear is

given by equation 3.

�� (3)

where; P is the force acting along the screw (10 N/m2), Perm.

is the permissible mean nut pressure.

Ø=H/dp = 1.2 to 2.5 for unsplit nuts and H is the nut

thickness Taking Ø= 2.0 and Perm = 0.80 kN/cm2 (for steel

screw, cast iron nut). From equation 3, the pitch diameter for

the threaded wear is calculated as = 2.0 mm. This is less than

the specified pitch diameter of 20 mm.

2.1.4. Motor (Power Requirement)

�� (4)

�� !"�� (5)

�� #"$!%&'�!"�� (6)

�� (�)��* (7)

�� +,�� -, (8)

�� ./01 (9)

P is the design force (10 kN), D is the inner diameter

(0.016 m) and N is the number of revolution per minute (100

rpm). The theoretical power requirement is calculated as 0.85

W from equation 9. Using a safety factor of 2.5, a 2 kW

electric motor is selected. The developed mechanical

pelletizer powered by an electric motor (Figure 2) was used

for the pelletizing process. Pellet sizes was in the range of (2

– 6 mm) according to the 3 different mesh sizes (2, 4 and 6

mm) in order to prevent nutrient loss from the soil.

2.1.5. Pelleting Efficiency

The pelletizing efficiency is given by equation 10

2 � 3435

� 100% (10)

where; wo is the total mass of pellets produced (g) and wi is

the total mass of input manure (g).

Figure 2. The Developed Pelletizer.

3. Results

The mesh sizes, mass of pellets produced as well as

efficiency of conversion of input manure to pellets at

different rotational speed of 150, 200 and 250 rpm is

presented in Tables 1, 2 and 3 respectively.

Table 1. Pelletizing Efficiency of Manure at 150 rpm.

S/N Mesh size (mm) Mass of

Pellets (g)

Mass of Input

Manure (g)

Efficiency

(%)

1 2 10.05 15 67

2 4 10.99 15 73.2

3 6 11.00 15 73.33

The pelletizing efficiency is the percentage ratio of

recovered pellets to the total weight of manure fed in. From

Table 1, it was observed that pelletizing efficiency increases as

mesh size increases at a speed of 150 rpm. Some of the manure

got stuck as a result of decreasing mesh size, hence the total

mass of output pellets increases as mesh size increases (Figure

3). The only demerit is that the rate of decomposition of

manure when applied on soil increases as mass of pellets

decreases. The pelletizing efficiency at 150 rpm for mesh sizes

2 mm, 4 mm and 6 mm is shown in Figure 3.

47 Ilesanmi Afolabi Daniyan and Omokhuale Marcus Akhere: Development of a Multi

Feed Pelletizer for the Production of Organic Fertilizer

Figure 3. Pelletizing Efficiency at 150 rpm for different Mesh Sizes.



Pellets (g)

Mass of Input

Manure (g)

Efficiency

(%)

1 2 10.65 15 71

2 4 11.1 15 74

3 6 11.4 15 76

From Table 2, it was observed that pelletizing efficiency

increases as the mesh size increases. Some of the manure got

stuck as a result of decreasing mesh size, hence the total mass

of output pellets increases as mesh size increases (Figure 4).

The pelletizing efficiency also tends to increase as the

rotational speed of the motor increases from 150 to 200 rpm.

The pelletizing efficiency at 200 rpm for mesh sizes 2 mm, 4

mm and 6 mm is shown in Figure 4.




Pellets (g)

Mass of Input

Manure (g)

Efficiency

(%)

1 2 10.40 15 69.3

2 4 11.01 15 73.4

3 6 11.25 15 75

From Table 3, it was observed that pelletizing efficiency

also increases as the mesh size increases, hence the total mass

of output pellets increases as mesh size increases (Figure 5).

The pelletizing efficiency at 200 rpm for mesh sizes 2 mm,

4 mm and 6 mm is shown in Figure 5.

The pelletizing efficiency at 250 rpm was found to be

greater than that of 150 rpm but lower than the pelletizing

efficiency at 200 rpm. The motion supplied by the motor at

the speed of 150 rpm may not be sufficient for the optimum

pellet formation of the manure. Increase in the speed of the

motor up to 200 rpm was observed to be sufficient resulting

in high pelletizing efficiency compared to other efficiencies

at the speeds 150 and 250 rpm (Figure 6). Gradual decrease

in the pelletizing efficiency was observed with further

increase in the speed of the electric motor beyond 200 rpm to

250 rpm. Excessive speed of the electric motor beyond the

optimum (200 rpm) was observed to decrease the pelletizing

efficiency due to agitation of the pelletizer.


Figure 6. Pelletizing Efficiency at 150, 200 and 250 rpm for different Mesh

Sizes.

The optimum rotational speed of the electric motor was

found to be 200 rpm. The pelletized manure at 200 rpm using

6 mm, 4 mm and 2 mm mesh sizes is presented in Figures 7,

8 and 9 respectively.

Figure 7. Pelletized Manure using 6 mm mesh.


American Journal of Mechanical and Materials Engineering 2017; 1(2): 44-48 48


4. Conclusion

The pelletizing machine for the production of organic

fertilizer plant was successfully designed and fabricated. It

consists of an integrated system of a single phase 3 kW

electric motor, 50 mm shaft, screw auger, pelletizer barrel,

ball bearing, pulley, 8 mm thick V-belt. Pellet sizes of

organic fertilizer produced was in the range of (2 – 6 mm)

according to the 3 different mesh sizes (2, 4 and 6 mm). The

total mass of pellets increases as mesh size increases, hence

pelleting efficiency also increases with increase in mesh

sizes. The optimum rotational speed of the electric motor was

found to be 200 rpm. The pelletizing efficiency increases

with increase in rotational speed up to 200 rpm and deceases

beyond this speed due to excessive agitation.

References

[1] Aremu, (2014). Development and testing of screw type kenaf (Hibiscus Cannabinus) pelletizing machine. Journal of Agricultural Technology. 10(4):803-815.

[2] Erickson S. and Prior M. (1990). The Briquetting of Agricultural Wastes for Fuel. FAO Environment and energy Paper 11. FAO, Via delle Terme di Caracalla, 00100 Rome, Italy; 1990.

[3] Hammed, T. B. (2013). The effect of locally fabricated pelletizing machine on the chemical and microbial composition of organic fertilizer. British Biotechnology 3(1):29-38.

[4] Hernandez G., Dominguez-Dominguez J. and Alvarado-Mancilla O. (2006). An Easy Laboratory Method for optimizing the Parameters for the Mechanical Densification Process: An Evaluation with an Extruder. Agri. Eng. Int. the CIGR E j. Manuscript PM 06 015:8.

[5] Hochmuth, R. C., Hochmuth, G. J., Hornsby, J. L. and Hodge, C. H. (1997). Comparison of different commercial fertilizer and poultry manure rates and combinations in the production of eggplant. Report 97-20, Suwannee Valley REC Extention.

[6] Holden, C. (1990). Process technology and market development for composted poultry manure: An overview of challenges and opportunities. Proc. 1990 National Poultry Waste Management Symposium, pp.236-242.

[7] Khurmi, R. S. (2008). Applied Mechanics and Strength of Materials. Chand Publishing Company, New Delhi.

[8] Mansell G. P., Syers, J. K. and Gregg, P. E. H. (1981). Soil Biol. Biochem. pp. 13:163-167.

[9] Moore, P. A., Daniel, T. C., Sharpley, A. N. and Wood, A. N. (1991). Poultry manure management. pp. 1-10., Arkansas Agricultural Experiment Station.

[10] Reza-Bagheri, Gholam A, Mohammad H, Zinol A. S. and Mehdi-Younessi H. (2011). The effect of pellet fertilizer application on corn yield and its components. African Journal of Agricultural Research. 6(10):2364-2371.

[11] Ryder, G. A. (1977) Strength of Materials. The Macmillan Press Ltd., London.

[12] Willson, G. B. (1989). Combining raw materials for composting. Biocycle, August, pp. 82-85.

development of a multi feed pelletizer for the production...

Documents